1. Field of the Invention
This invention relates to a warning system for vehicles, and more particularly to a warning system of this kind, which measures the distance from an object such as a preceding vehicle and issues a warning when the vehicle approaches the object.
2. Prior Art
Conventionally, there have been proposed a warning system for vehicles, which measures or detects the distance between the source vehicle and a preceding vehicle or the like by means of a laser beam while the source vehicle is traveling, and issues a warning to alert the driver when the measured distance becomes smaller than a safety distance determined from the braking distance and free running distance of the vehicle (Japanese Provisional Patent Publication (Kokai) No. 4-213800, and a warning system which exchanges by wireless data on the present location, traveling speed and traveling direction between the source vehicle and neighboring vehicles, and issues a warning when a collision of the source vehicle with a neighboring vehicle at a crossing (Japanese Provisional Patent Publication (Kokai) No. 4-290200).
However, the conventional warning systems do not contemplate the fact that the driver's reaction time, i.e. the time period from the time a warning is issued to the time the driver actually operates the brake or the like varies depending upon the driver. As a result, the driver cannot always operate the brake or the like at appropriate timing in response to a warning issued, such that the timing of issue of a warning is too early to one driver, while it is too late to another driver.